Punctureproof fuel cell



Feb. 18, 1947. w, c, s n- L 2,416,231

PUNCTURE-PROOF FUED CELL Filed April 12, 1944 GASOLINE RESISTANT LAYER SEAL.

' REINFORCING FABRIC FIG-2 1 fumrso STATE Patented Feb. 18, 19 47 s 'PATEN T OFFICE rUNcTUnErRooF FUEL can.

. Winthrope Q Smith, Elizabeth, and Joseph P.

.Haworth, Westfleld, N. J., assignorato Standard Oil Development Company, a corporation of Delaware Application 1112, 1944 Serial N6. 530,708

' This invention relates-to fuel containers, re-

12 Claims. (01.154-435) lates particularly to gasoline tanks for airplanes;

and relates especially to the swellant layer in puncture-proof airplane gasoline tanks; and to I means for maintaining the puncture-proof properties of the tanks even at temperatures below zero.

fabric and. rubbery materials which are fitted into appropriate locations in the plane, usually in the Airplanegasoline tanks, especially on military and combat planes, consists. of cells prepared from 2 gasoline-resistant inner layer and the oil-resistant outer layer which is swellable rapidly by gasoline over a temperature range from 125", F. to

--60 F. without becoming sufllciently stifl to wings. Each cell consists'of a eas'olineesistant inner liner to hold the fuel; and an outer layer of reinforcing.structure consisting of a heavy ,fabriccoated on the outside with oil-resistant abrasive-resistant rubbery compound to protect the cell against oil, fuel or friction which might injur'ethe cell when stowed away in the wingof the plane. Between the inner gasoline-resistant liner, and the-outer protective layer, there is placed a swellable sealing compound, usually reinforced by additional fabric. 'A bullet or other bit of metal driven through the wall of the cell I Q will make a hole through which the fuel can.

leak; However, the interposed layer of swellable compound absorbs gasoline and swells sufficiently from the absorbed gasoline to close the hole.

- In the past.1a layer of poly-chloroprene or of the interpolymer "of butadiene and acrylonitrile has been used as the inner. liner; and a layer of similar'material, reinforced with fabric has been used for the outer layer; with a layer of natural natural rubber has made it necessary to find a 'fsubstitute for natural rubber. Such compounds as poly-chloroprene and the interpolymer of bu.- tadiene and acrylonitrile do not swell inthepresence of gasoline; and while the interpolymer of butadiene and styrene shows much better swellin properties, it isdiflicult to fabricate it into afuel cell under proper conditions for utilizing the swelling; furthermore. of the other available elastic, plastic substances, only the low temperature interpolyme'r of isobutylene with'a diolefln shows s'uflicient strength, sufficient ease of fabrication,

and sufllciently rapid swelling properties to be a satisfactory swellant layer. However,- this polymer shows a poor freeze resistance, and at temperatures-below about 0 C., it becomes so stiff that the passage of a bullet through itresults ma shattering-of the fuel-cell so great that the polymer cannot swell 'sufllciently to close the hole. 1 Thus the'present invention provides a synthetic sealing member for use interposed between the :rubber, reinforced with fabric for the interposed swellable layer. However, .theQunavailability of Recipe #1 I v .1

Parts Butadiene acrylonitrile copolymer 100 Carbon black v Zinc oxide 5 Stearic acid 1 Sulfur v1.5

-- Benzothiazyl disulfide e 1.0 Dibutyl phthalate 20.0

shatter under the impact of a rifle bullet.

According to the present invention, there is' used for fuel cells the inner sealing layer of poly-chloroprene or the polymer of butadiene and acrylonitrile, and the outer layer of fabric coated with oil-resistant, abrasive-re-istant material; with an interposed layer of the low temperature interpolymer of isobutylene with a diolefin which is compounded with a substantial proportion of a highly 'parafllnic hydrocarbon oil having a boiling point within the range between 200 F. and 700 F. This paramnic hydrocarbon oil improves the shatter-resistance of the interlowing description when read in connection with I the accomp ny ng drawing wherein Fig. 1 is a view in elevation, partly in section, of an-airplane fuel cell, and r Fig. 2 is a sectional view of the successive layers of the body of which the fuel cell'is constructed. Referring to the figures, the fuel cell l with filler fittings I and outlet fittings 3 contains a substantial quantity of gasoline fuel I. The body of the fuel cell is formed with an inner layer! which is gasoline-resistant and preferably convsists'of alamina of butadiene acrylonitrile compounded with the usual compounding agents including carbon black, zinc oxide,etc. A suitable recipe is as follows:

Alternatively, the layer 5' may consist of the. interpolymer of polychloroprene compounded with the usual components ,the' following recipe which is representative of suitable compounding recipes:

. endered onto the fabric 1.

. I Parts Polychloroprenes 100 Carbon black 50 Zinc oxide- 5 Stearic acid--. 1 Extra light calcined magnesia 4.0 Dibutyl p te 5.0

diene and acrylonitrile is particularly satisfactory for this outer layer and it may be prepared according to the recipe above given and sheeted out on the calender. A layer of fabric 1 is likewise provided for strengthening and reinforcing purposes; the outer layer 6 being preferably cal- Between the layers 5 and 6 there is provided a swellant or sealant layer 8having a second layer of fabric 9 incorporated into the swellant layer.

, The swellant layer preferably consists of an interpolymer of an isoolefin such as isobutylene with a polyolefin such as butadiene or isoprene or the like, prepared by a Friedel-Crafts catalyst polymerization at low temperature. This sealant layer is compounded with appropriate substances for improving the tensile strength, for curing; and the like; and, in addition, it contains a substantial portion of a moderately heavy hydrocarbon oil to produce \resistance to shattering when shot at low temperatures.

In preparing the swellant layer, the components preferably consist of isobutylene as a first component, although other. isooleflns such as 2, methyl butenel, or 2, methyl pentene-l. or 2, m thyl hexene-l may, under some circumstances, be used, The second'component of the mixture is a polyoleiin such as 'butadiene or isoprene or piperylene or dimethyl butadiene, or dimethallyl or myrcene;.nr the like; substantially any of the atoms priate refrigerant. The refrigerant may be used in a refrigerating jacket applied to the reactor or may be admixedfdirectly'with the polymerizable olefins. In the latter instance, such substances as liquid propane, liquid ethane, liquid ethylene and even liquid methane are usable, as well as solid or liquid carbon dioxide. When the refriger ant is used'in a refrigerating jacket, practically any of the low boiling substances such as the refrigerants above-mentioned, and, in addition, substances such as sulfur dioxide under reduced pressuch as are shown in polymer is a basic sure, or methyl chloride under reduced pressure, I or liquid carbon dioxide or other substances under non-complex-forming solvent such as ethyl or methyl chloride or the like. For theFriedel- Crafts .type catalyst, substantially any" of the Friedel-Crafts catalyst disclosed by N. O. Calloway in hisarticle on The Friedel-Crafts synthesis" printed in the issue of "Chemical Reviews published for the American Chemical Society at Baltimore in 1935 in vol. XVII, N0. 3, pages 327-375 may be used as a catalyst. For the catalyst solvent, substantially any of the mono or polyalkyl halides which have freezing points below 0 C. may be used, these being identifled as low freezing" because they freeze at temperatures below room temperature, all of them being characterized by their freedom from any tendency to form complexes or addition compounds with a metal halide.

I The catalyst solution is dispersed as rapidly as possible into the cold olefinic material; preferably by application in the form of a fine spray to the surface of the rapidlystirred, cold, olefinic mixture. Alternatively, however, the catalyst solution may be delivered as a jet into a zone of high turbulence such as forms behind the blades of a stirrer and by other means which will be obvious to those skilled\ in the art, the principal requirement being rapid dispersion of the catalyst into the olefinic mixture. The polymerization is preferably halted short of the complete polymerization of all of the olefin i0 material present. This may be accomplished merely by suspending the delivery of catalyst solution; or the polymerization mixture may be dumped into a catalyst-quenching agent such as warm water or warm alkaline solution or warm alcohol solution or the like. In any event, the solid polymer is brought up to room temperature and purified, if desired, by washing on the roll mill or in the kneadcr or by other convenient means. This material for the tank swellant member. l

The'polymer as prepared, can be conveniently compounded according to the following recipe:

Recipe #3 Copolymer l 2 3 Parts by Parts by Paris by weight weight wei'lhi Copolymer 100 l00-0 Zinc oxide 5 5 5 St micacid 1.5 1.5 1.5 'lunds (tctrnnlcthyl tlliurnm disulv V iidc) .L 1.0 1.0 1.0

Mercuptoben' till l "1111' 0.5 0.5 0.5 Sulfur 1.5 1.5 1.5 laraflinic 20-60 20-60 20-fi0 (last-ox (carbon black). 54 5441 l'rccurcdco iolymcr (1-100 The above recipes are representative, and may be varied both in proportions and in components in many 'wayswhich will be obvious to. those skilledin the art without departing from the inventive concept here disclosed.

The hydrocarbon oil, the presence of which in this recipe is of the essence of the invention, is

preferably a paraffinic type petroleum oil having a boiling point preferably between about 300 C.

and 500" F. It is desirable that this oil be one afflnic oils without acid treatment having the.

same boiling range, such as kerosene, are also usable, satisfactory and effective, although they do not give quite' as good results as the purified oils.

The presence of the purified parafiinic oil yieldsthe new and unexpected result that the resulting compound remains elastic at temperatures aslow as --60 F., or even lower, without reducing its swelling properties in the presence of gasoline, and without substantial reduction in tensile strength and other physical properties of the polymer.

The precured copolymer listed in the above formula is prepared by compounding the copolymer of isobutylene and a polyolefin, with a curing agent which may be sulfur, or sulfur with a curing aid such as tetramethyl thiuram disulfide, and the like, cured by an appropriate heat treatment and re-plasticized on a cold roll mill. The

. presence of the precured copolymer is of substantial advantage infactory processing because of the fact that the presence of relatively large amounts of the purified parafflnic hydrocarbon oil causes the stock to become very soft'and flowable under its own weight. The presence in the mixture of precured and re-plasticizedpolymer increases the stiffness and physical strength of the composition to such an extent that it is more easily handled on the mill and in the course of the assembly of the fuel cells. The presence of the precured copolymer does not reduce the physical strength of the cured material, does not vreduce the shatter resistance at low temperaturesand in some instances, substantially increases the physical strength of the compound. Also the presence of the precured polymer somewhat impr'ovesthe adhesion between the gasoline-resistant layer and the swellant layer and between the oil and friction-resistant layer and the swellant layer.

In some instances, the several layers may be assembled and cured together with suflicient adhesion between them for the production of a sat isfactory fuel cell; especially if the precured polymer is included in the compounding recipe. In other instances, especially when none of the precured polymer is included in the swellant layer, a tie ply is advantageous between the several layers. This tie ply mayconveniently consist of a mixture of the materials used for the outer layers with precured and re-plasticized copolymer. For this purpose the raw copolymer is desirably compounded with curing agents such as sulfur, or

, sulfur with a sulfurization aid; or with para quin- .one dioxime or its esters, or para dinitroso cymene or its analogs or homologs or esters.

With the latter curing agent, the compounding-may be conducted on a cool mill, and the curing and replasticizing conducted simultaneously on the same mill at a higher temperature, -in view of the very rapid curing effect of the nitroso curing agents. g

When the curing is complete, the desired second component such as polychloroprene or the copolymer of butadiene with acrylonitrile may be' milled into the replasticized copolymer and the material sheeted out and interposed between the main layers during the course of the preparation.

of the fuel cell. Alternatively, the material of the tie ply may be prepared in solution, the nec:

essary curing agents being dissolved in the solu-* tion, and the main laminae are then treated on,

their surfaces with the solution, the solvent evaporated and the laminae placed, to ether in the desired structure.

To indicate the difficulties encountered in the preparation offuel cells for servlce at extremely low stratosphere temperatures, a fuel cell was prepared, as shown in Fig, 1, the inner layer of which consisted of a lamina of the butadieneacrylonitrile copolymer compounded according-to Recipe #1 and cured as indicated. The'intermediate layer consisted of a polymer of isobutylene and isoprene prepared as above described,

compounded according to item 1 of Recipe #3,

but without the paramnic oil. This compound i was prepared on the roll mill and calendered onto both sides of the fabric 9. An outer layer for the fuel cell was prepared according to recipe #1, calendered onto the fabric 1 and a skim coating of the same compound was applied to the in-; These several laminae were assembled with the aid of the previously described tie ply cements into a fuel cell and placed in the mold. Th'assembled cell was then cured under heat and pressure for the appropri the ate length of time, and then removed from mold.

The cell was then filled nearly full of aviation gasoline, the cell and its contents cooled to 50 C., and a .45 calibre rifiabullet was fired into the cell at point blank range at the low temperature.

In the absence of the parafiinic oil in the sealant layer, all of the lamina includingthis sealant-or swellant layer shattered, leaving a large hole in the fuel cell which could not be closed by swell;- ing of the sealant layer, with the consequence that considerable quantities of gasoline were lost from the cell under conditions which, if they had occurred in the airplane, would result in avery severe fire hazard.

Earample 1 A similar fuel cell was prepared utilizing an inner lamina of butadiene-acry1onitrile compounded according to Recipe #1; an intermediate lamina of the copolymerof isobutylene and isoprene prepared as above described and compounded according to item 1 of Recipe #3, using 30 parts of the hydrocarbon oil'and calendered onto fabric 9 as before, with an outer layer of the same butadiene-acrylonitrile compoundealendered onto fabric as before. *Thes' several the production of only a small hole in which the laminae were assembled; into a cell, as*above swelling effect of the gasoline in the cell uponthe exposed sealant layer caused an immediate closing of the hole. The sealing of the tank was sufficiently rapid to allow only a momentary dampnessof gasoline on the outsideof the tank atth'e H entrance andexit points of each bullet." No'sub stantial loss of gasoline occurred and no fire hazard was produced. The same tank and its ,contents were then warmed to. approximately F. and a second series of .45 calibre rifle eral compositions here shown.

, 7 bullets were fired through the tank. At th temperature also, immediate sealing of the punctures resulted and no more gasoline was lost from the tank than had occurred at the low temperature.

The tank and its contents were then again cooled to 60 C. and a third series of .45 calibre rifle bullets were fired through the tank. In this instance also, prompt and effective sealing occurred, negligible quantities, amounting only to a momentary dampness being found outside of the cell.

These tests show the efiicacy of the sealing ac tion at any temperature between -60 F. and +125 F. when the sealant layer contained incorporated hydrocarbon oil as in Recipe #3.

Reports from combat areas further indicate that this effective sealing action is maintained under combat conditions.

Example 2 A similar fuel cell was prepared utilizing for the inner layer the poly-chloroprene compound of Recipe #2, utilizing for the swellant layer item 3 of Recipe #3 with 30 parts of oil, calendercd onto fabric 9 with an outer layer of poly-chloroprene compounded according to Recipe #3 and calendered onto the fabric 1. were particularly easy to assemble because of the presence in the swellant layer of the precured polymer which simplified the assembly problems and yielded a tougher, more durable cell.

Rifle tests, made as described in- Example 1, showed an equally high sealing action, and no perceptible difference in leakage of gasoline was 1 found at any temperature as between the two fuel cells of Example 2 and Example 1.

The presence of the precured polymer in the 1 laminae of this cell greatly improved the han- 1 the polymer either at low or hightemperatures.

Example 3 A series of similar fuel cells were prepared 1 utilizing various other arrangements of the sev- One of these utilized an inner lamina of poly-chloroprene, an .outer lamina of the interpolymer of butadiene and acrylonitrile and a middle layer of the iso- ;butylene-isoprene interpolymer, all accordingto Recipes 1, 2 and 3, above set out; the isobutyleneisoprene low-temperature polymer recipe having approximately parts of kerosene incorporated,

but without either carbonblack or precured co- ,polymer. This cell proved to"be somewhat difficult to fabricate because of the fragile character 10f the middle lamina. However, by careful work a fully satisfactory cell was obtained which, upon testing at temperatures between 60 F. and j+125 F. as above indicated, showed fully adequate and satisfactory sealing when .45 calibre ;bullets were fired through the cell.

Another cell was prepared usingpoly-chloro-- These laminae The presence of the precured copolymer I atures as low as F.

prene for the inner layer and the copolymer of b'utadiene and acrylonitrile for the outer layer I with a middle layer according to Recipe 3 using l item 3 containing both carbon black and precured g copolymer; with approximately 20 parts of acid purified hydrocarbon oil; specifically, acid purified kerosene. This combination of laminae, prepared, as above outlined, proved to be particularly easy to assemble because of the noticeably higher strength of the middle layer because of the presence of the precured copolymer and carbon black, and the smaller quantity of oil. Upon firing tests, this combination also sealed entirely satisfactorily, although there was some possibility of a fraction of a second slower action.

Other combinations of these severalpolymers also were tried using various combinations of the several outer and inner layer recipes with the several items of Recipe #3 for the copolymer, and it was found that considerable latitude of construction was available without sacrifice of efliciency. or effectiveness 'of sealing. Approximately the minimum amount of the purified parafiinic hydrocarbon which would give immediate sealing and no shattering at 60 F. was about 20 parts of oil per parts of polymer. How-- ever, where the minimum temperature to be encountered was only -20 F. to 30 F., amounts of oil as small as 540% would give sufiicient resistance to shattering to' make the cell satisfactory under these milder temperature extremes;

and accordingly, it appears that the minimum significant amount is probably two or three parts of hydrocarbon oil per 100 of polymer for moderately low temperature service. At the other extreme, amounts of hydrocarbon oil as high as 50 or 60 parts per 100 of polymer are usable and prevent shatter at temperatures as low as may be desired. It is, however, somewhat difficult to construct the cells from material containing such high proportions-of paraflinic oil. It is found, however, that by very careful handling, the use of substantial quantities of precured copolymer and substantial quantities of filler, amounts of oil up to about '75 parts per 100 of raw polymer can be used. Above these values the difficulty of handling becomes so great as to be commercially unfeasible, although for special service where cost and difficulty of assembly are not factors, somewhat higher amounts can be used. Thus the invention consists of a fuel cell having outer and inner oil-and-gasolineresistant laminae and an interposed swellant lamina consisting of a, copolymer of isobutylene .with a polyolefin containing dissolved therein a aflinic hydrocarbon oil; the resulting fuel cell showing highly satisfactory, effective, and efficient sealing action against punctures at temperatures from +100 to F. down to temper- While there are above disclosedbut a limited number of embodimentsof the invention, it is possible to produce still other embodiments without departing from the inventive concept herein disclosed and it is, therefore, desired that only such limitations be imposed upon the appended claims as are stated therein. a

The invention claimed is:

1. A fuelcell comprising a plurality of lamina layers, one thereof'being an inner layer of plastic, elastic, gasolineresistant material, another thereof being an outer layer of plastic, elastic, oil-resistant, abrasioneresistant material and an interposed lamina comprising a, cured polymer of isobutylene witha diolefi'n containing therein a purified parafiinic hydrocarbon oil.

2. A fuel cell ccmprisinga plurality of lamina purified par- I elastic, gasoline-resistant material,

layers, one thereof being an inner layer of plastic, elastic, gasoline-resistant material, another thereof being an outerlayer of plastic, elastic, oil-resistant, abrasion-resistant material and an interposed lamina comprising a cufed polymer of isobutylene with a diolefin containing therein a purified paraffinic-hydrocarbon oil, the combination being characterized by the capability of holding gasoline, the property of swelling when punctured to prevent leakage of gasoline, and the property of swelling to prevent leakage of gasoline at any temperature between -60 F. and +l25 F.

3. A fuel cell comprising a pluralityof lamina layers, one thereof being an inner elastic, gasoline-resistant material, another thereof being'an outer layer of plastic, elastic, oil-resistant, abrasion-resistant material having a layer of reinforcing fabric therein and an interposed lamina, comprising a cured polymer of isobutylene with adiolefin containing therein a purified parafilnic hydrocarbon oil, the combination being characterized by the capability of holding gasoline, the property of swelling when punctured to prevent leakage of gasoline, and the property of swelling when punctured to prevent leakage of gasoline at any temperature between -60 F. and 125 F.

4. A fuel cell comprising a plurality of lamina layers, one thereof being an inner layer of plastic, another thereof being an outer layer of plastic, elastic, oil-resistant, abrasion-resistant material having a layer of reinforcing fabric therein; and an interposed sealant lamina comprising a cured polymer of isobutylene with a, diolefln having a second layer of fabric therein; and containing a purified paraffinic hydrocarbon oil, the combination being characterized by the capability of holding gasoline, the property of swelling when punctured to prevent leakage of gasoline, and the property of swelling when punctured to prevent leakage of gasoline at any temperature between -60 F. and +125 F. I

'5. A fuel cell comprising a plurality of lamina layers, one thereof being an inner layer of plastic, elastic, gasoline-resistant material, another thereof being an outer layer of plastic, .elastic,

oil-resistant, abrasion-resistant material having a layer of reinforcing fabric therein; ancl an interposed sealant lamina comprising a cured polymer of isobutylene with a diolefin; the said sealant lamina containing therein a purified paraijflnic hydrocarbon oil, the combination being characterized by the capability of holding gasoline, the

property of swelling when punctured to prevent leakage of gasoline, and the propertycf swelling to prevent leakage of gasoline at any temperature between -60 F. and +125 F.

, 6. A fuel cell comprising a plurality of lamina layers,'one thereof being an inner layer of plastic, elastic, gasoline-resistant material, another ing an interpolymer layers, one thereof tic. elastic, gasoline-resistant material comprisof butadiene and acrylonitrile, another thereof being an outer layer of plastic, elastic, oil-resistant, abrasion-resistant material having a layer of reinforcing fabric therein and an interposed lamina comprising a 'cured polymer of isobutylene with a diolefln conlayer of plastic,

taining therein a purified parafflnic hydrocarbon oil, the combination being characterized bylthe capability of holding gasoline, the property of swelling when punctured to prevent leakage of gasoline at any temperature between -60 F. and +125 F. i

8. A fuel cell co elastic, gasoline-resistant material, thereof being an outer layer of plastic, elastic, oil-resistant, abrasion-resistant material comprising an interpolymer of butadiene and acrylonitrile having a layer of reinforcing fabric therein; and an interposed lamina comprising a cured polymer of isobutylene with a diolefln containing therein a purified paraiilnic hydrocarbon oil, the

leakage of gasoline, and swelling to prevent leakage of temperature between -60 F.

tic, elastic, gasoline-resistant material, another thereof being an outer layer of plastic, elastic, oil-resistant, abrasion-resistant material having a layer of reinforcing fabric therein and an interposed lamina comprisinga cured polymer of isobutylene with a diolefin containing therein a parafllnic hydrocarbon 011' comprising purified thereof-being an outer layer of plastic, elastic,

oil-resistant, abrasion-resistant material having a layer of reinforcing fabric therein and an interposed sealant lamina comprising a cured polymer of isobutylene with a diole'fln; the said sealantflaminahaying a fabricin the polymer layer, and containing therein a purified parafilnic hydrocarbon oil, the combination being characterized by the capability of holding gasoline, the property of swelling when punctured to prevent leakage of gasoline, and the property of swelling to prevent leakage of gasoline at any temperature between .60 F. and +l25 F.

,7. A fuel cell comprising a plurality of lamina kerosene, the combination being characterized by the capability of holding gasoline, the property of swelling when punctured to prevent leakage of gasoline, and the property of swelling to prevent leakage of gasoline at any temperature between 60 F. and F 10. A fuel cell comprisinga plurality of lamina layers, one thereof being an inner layer of plastic,-elastic, gasoline-resistant material, another thereof being anouter layer of plastic, elastic, oilresistant, abrasion-resistant 'material having a layer of reinforcing fabric therein and an interposed lamina comprising a cured polymer of isobutylene with a diolefin containing therein a puri fled paraffinic hydrocarbon oil, the combination being characterized by the capability of holding gasoline, the property of swelling when punctured to prevent leakage of gasoline, and the property of swelling to prevent leakage of gasoline at any temperature between -60 F. and +125 F., the several layers having compounded thereinto carboililblgck, zincoxide and stearic acid.

layers, one thereof being an elastic, gasoline-resistant material, another thereof being an outer layer of plastic, elastic, oil-resistant, abrasion-resistant material having alayer of reinforcing fabric therein and an interposed'lamina comprising a cured polymer of gasoline at any temperature between isobutylene with 'a diolefin containing therein a purifiedparafiinic hydrocarbon oil, the combination being characterized by the capability of holding gasoline, the property of swelling when punctured to prevent leakage of gasoline, and the property of swelling to prevent leakage of so F, and.

being an inner layer of'plas- 7 V prising a plurality of lamina layers, one thereof being an inner layer of plastic, another property of swelling when" fuel cell comprising aplurality of lamina inner layer of plastic,

a a layerof reinforcing I 11 I +125 F., the several layers having compounded thereinto carbon black, zinc oxide and stearic acid, the interposed polymer also having precured,

and replasticized polymer compounded'thereinto. 12. A fuel cell comprising a. plurality of lamina.

layers, one thereof being an inner layer of plastic,

elastic, gasoline-resistant material, another thereof being an outerlayerof plastic, elastic, oil-resistant; abrasion-resistant material having fabric therein and an interposed lamina. comprising a cured polymer of 'isobutylene with a diolefln containing therein a purified; parafllnic hydrocarbon oil, the combination being characterized by the'capability of holding gasoline, the property of swelling when punctured to prevent leakage of gasoline, and the property'of swelling to prevent leaakge'of gasoline at any temperature between 60 F. and +1 25 F., the several layers having compounded thereinto carbon black, zinc oxide and stearic acid, the several laminas being held together by a tie ply. v

WINTHROPE C. SMITH. JOSEPH P. HAWORTH.

REFERENCES CITED The following references are of record-in the file of this patent: I

FOREIGN PATENTS Number Country Date 538,873 British Aug'. 20, 1941 538,794 British Aug. 18, 1941 539,150 Aug. 29; 1941,

British 

